Modern vehicles are generally equipped with numerous sensors, such as, for example, oil pressure, coolant temperature, transmission temperature, engine temperature, steering position, air/fuel ratio, etc. Typically, the sensors are connected to an on-board computer control module that continually monitors the sensors and regulates the vehicles functions accordingly. Generally the information generated by the sensor is continually passed along the vehicle data link as part of the vehicle diagnostic system. The vehicle diagnostic system cooperates with the factory installed gauge cluster to provide failure fault indications to the driver in the form of a “service engine” light. The vehicle diagnostic system typically includes one or more separate computer control modules. Examples of such computer control modules (also known as just “modules”) are: a power train control module (PCM), an engine control module (ECM), a transmission control module (TCM), an anti-lock brake system (ABS) control module, and an air bag control module. Typically the computer control modules are connected together by a data link, forming the vehicle diagnostic system. The data link typically has a connection point, or data link connector (DLC) that is normally located under the dash of the vehicle. The vehicle diagnostic system is generally used to provide relevant information to repair technicians. The DLC provides repair technicians with a place to connect off-board vehicle diagnostic devices, such as scan tools and code readers for communication with the vehicle diagnostic system.
Typically, scan tools are capable of performing at least some of the following major functions: “View Data,” also known as “Live Data,” “Data,” and “Data Test, DTC” (viewing and displaying in real-time live changing data from a plurality of module sensors), display of textual diagnosis descriptions corresponding to the various diagnostic codes, recording and playback of data, device control (manually controlling modules for diagnostic purposes), and reading and displaying vehicle information from the vehicle's computer (e.g., VIN information, controller calibration identification number, etc.).